Respiratory medication is widely administered to patients, especially asthmatics, using devices known as inhalers. An inhaler can take several forms, including an aerosol-powered, metered dose inhaler and a dry powder inhaler. Usually, a dry powder inhaler is powered using the patient""s inhalation effort, the inhaler being both triggered and powered by the inhalation. An inhaler is usually used by a patient without supervision, this use usually being on a regular basis after an initial training period.
It is important that an inhaler is used properly, as the efficiency and efficacy of an inhaler is dependent on the patient""s technique. Devices are known for aiding the training of a patient in the use of an inhaler. When training, the rate of inhalation of the patient is important, as too fast or too soft an effort will result in the medication not reaching the optimum distribution in the airways of the patient""s respiratory system. Typically, a known training device uses a placebo in place of respiratory medication, and the training device is used, under supervision, to get the patient used to inhaling as close to the optimum rate for a given inhaler. Once the patient has a good compliance of the effort required, the training device is replaced by the appropriate inhaler.
The aim of the invention is to provide a device that can indicate to a patient when his inhalation flow rate has reached the optimum while that patient is using an inhaler.
The present invention provides a flow indicator for an inhaler, the flow indicator comprising a housing defining a mouthpiece, an inlet for connection to the product-dispensing chamber of an inhaler, a chamber positioned between the inlet and the mouthpiece of the indicator, and an indicator member movably mounted in the chamber in such a manner that inhalation at the mouthpiece of the indicator causes the indicator member to move within the chamber, the indicator member being so mounted as to co-operate with a switch member associated with the housing to provide an indication when inhalation is at an optimum rate for a given inhaler attached to the inlet.
In a preferred embodiment, a vane pivotally mounted within the chamber constitutes the indicator member.
Advantageously, the vane carries a magnet, and the switch member is a magnetic reed switch, the magnet and the reed switch constituting a magnetic switch.
Alternatively, the vane carries a magnet, and the switch member is constituted by a plurality of magnetic reed switches attached to the housing, a first reed switch being mounted so as to be aligned with the magnet when inhalation is at said optimum rate, the other reed switches being positioned on opposite sides of said first reed switch to indicate to the user when the inhalation rate is lower or higher than said optimum rate, the magnet and any one of the reed switches constituting a magnetic switch.
Preferably, the vane carries a counterweight which is positioned on the opposite side of the pivot to the magnet.
A spring may be provided to bias the vane away from the position indicating an optimum inhalation rate and towards the inlet. Preferably, the spring has a predetermined spring rating adapted to the optimum inhalation rate for a given user. Advantageously, the spring is chosen from a plurality of springs, each of which has a different spring rating adapted to the optimum inhalation rate of a different user.
Preferably, the flow indicator is provided with an adaptor for connecting its inlet to the mouthpiece of an inhaler.
The invention also provides an inhaler incorporating a flow indicator as defined above, wherein the inhaler is aligned with a product-dispensing chamber forming part of the inhaler.